Just spitballing here...but striking at 162 sounds low to hit a mash of 154. IME I would strike closer to 168 to land at 154. Much easier to strike high and temper down w/ either cool water or a few ice cubes.
As far as gallons of sparge water, i always find it simpler to measure the amount of wort needed on the final sparge, and sparge w/ that amount to reach your intended pre boil volume. Example: It matters none what the calculator says if you need 3.5 gallons more wort...then sparge 3.5 gallons
edit...here is a handy very simple brewing calc...http://www.rackers.org/calcs.shtml
fwiw it shows a strike of 171 for a mash of 154.